All in the family: Uncovering the genetic history of the world's most lethal pathogens

They’re tiny terrors that are best known for the millions of people they’ve killed. Few us of would want to meet them, or their relatives. But for researchers like Verena J. Schuenemann, PhD, and Johannes Krause, PhD, uncovering the pedigrees of the world’s most lethal pathogens is an important step in combating the diseases we avoid like the plague.

Earlier this week in Forbes, writer John Farrell told the tale of the two scientists from the University of Tübingen in Germany, and how they hunt down some of the most notorious pathogens in history.

Studies such as work done by Schuenemann, Krause, and a team of international researchers on potato blight, the Black Death, and (most recently) leprosy, are changing our understanding of diseases that were once buried in the past. As Ann Gibbons of Science recently wrote (subscription required):

Awash in data, several labs are racing neck-and-neck to cull DNA from a Most Wanted list of legendary killers: tuberculosis (TB), plague, cholera, Leishmania, leprosy, the potato blight, and AIDS. They gather traces of these culprits from ancient teeth, bones, hair, feces, and—in the case of potato blight—from skin and leaves, then unleash the sequencers. The work, which began in earnest 3 years ago, adds a new dimension to our understanding of historical events, revealing the true nature of the villains responsible for humanity’s worst epidemics. “There are a lot of diseases described in the historical record that we don’t know what the pathogen is,” says molecular anthropologist Anne Stone of Arizona State University, Tempe.

One persistent question is how the deadliest pathogens evolve over time. As Farrell outlines in his piece, Schuenemann’s team found that the bacteria (Yersinia pestis) responsible for plagues in Africa today are genetically similar to the bacteria that unleashed the Black Death on Europeans in 1347. But, today’s plagues are less lethal – which suggests that evolution knocked a few teeth out of Black Death’s lethal bite.

Understanding when and how evolution changes a pathogen’s virulence is important because the plague is a re-emerging disease and history could repeat itself.

Holly MacCormick is a writing intern in the medical school’s Office of Communication & Public Affairs. She is a graduate student in ecology and evolutionary biology at University of California-Santa Cruz.